The sound editors used some of Mark's vocals along with the singers you see listed in the soundtrack/credits. Instead of just cutting and splicing sections, the editor mixed them together so you can't really hear Mark, it's a hybrid voice, which is why some of the songs in the movie sound a bit different than the soundtrack.

And my post from 2002 about the soundtrack vs. the film. Lianne Administrator posted June 01, 2002 12:52 AM

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If you look at the liner notes to the RS Soundtrack you would see:

Vocals by: Jeff Scott Soto for Living the Life, Stand Up and Wasted Generation

Vocals by: Mike Mitijavic for We All Die Young, Blood Pollution and Long Live Rock & Roll.

Vocals by: Brian Vander Ark for Colorful. He of the Verve Pipe.

[...] Mark's voice along with Mike and Jeff were mixed by the sound engineer in post production. While filming Mark was singing, but we don't hear just him.

And from MadameRubi

Quote:

New Member posted August 07, 2002 01:07 AM
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If you have the DVD and under the special features is the commentary option, which goes through the whole movie with the directors commentary and he states in there that Mark was doing some of the singing. But not very much since he has a much deeper voice than your average 80's rock singer. Anyway the commentary totally clears all that up and he even tells you at about which points Mark is really singing.

And technically Mark was a part of Nynuk - the original name for the group. It was only after they signed up with Columbia did they change it to Donnie's song - New Kids on the Block. And as markandme said he left way before they ever recorded anything.